Chain winders are well-known and are used to open and close windows which are hinged on a horizontal axis, typically at the top of the window. The advantage of using chain winders is that the chain itself also functions to hold the window in any position without any ability of the window to inadvertently slam to a closed position. Also, the chain winder prevents the window from being further opened, for instance by an intruder.
Known chain winders have a elongate housing in which the chain can be housed. The housing can have an internal curved track along which the chain can move. The housing has an opening through which the chain can pass, and a sprocket is provided in the housing and adjacent the opening. The sprocket has teeth which pass into the chain such that rotation of the sprocket in a forward direction forces the chain out of the housing while rotation of the sprocket in a backward direction forces the chain into the housing.
The sprocket is rotated by an external handle which can be gripped and turned to turn the sprocket and therefore to wind out or wind in the chain
From a security point of view it would be advantageous to have a lockable chain winder which can be locked by a key such that a window can be left in a partially open position and can be locked in place. However, a disadvantage with a lockable chain winder is that it is also generally necessary to insert the key to unlock the chain winder to enable the window to be closed. Thus, should it be desired to close the window (for instance, during rain, strong wind or in the evening), it is necessary to find the chain winder key, insert it to unlock the chain winder and then to rotate the handle.
If a number of windows are provided with lockable chain winders, this arrangement becomes unsatisfactory.